Streets, parking lots, and other paved surfaces for vehicular and pedestrian traffic are designed and built with storm drains or storm water inlets to drain the storm waters that these surfaces collect. On streets such drains often are located periodically along curbs and shoulders. Paved surfaces are typically graded in such a manner so that water falling onto the surface should flow to one or more of the storm drains. This prevents water from collecting on the surface and the attendant problems associated with flooding, such as inhibiting the flow of traffic, and spillover onto adjacent lands and structures.
A typical storm water inlet has a surface opening that sits above a vertical-walled chamber called a catch basin, which is connected to a sewer system by one or more pipes entering the chamber through openings in the vertical walls. In a common design the catch basin sits on the edge of a roadway inside of the curb, and the surface opening is covered with a grate. This grate enables water to flow into the catch basin but prevents large objects from passing into the catch basin and blocking the sewer pipe. Other designs are built into the curb and have a simple “fall-in” opening in the curb. Still other designs have a combination of these or other features. In virtually all storm water inlet designs, the catch basin is intended to collect debris that is washed in by the force of flowing water. As a result, storm water inlets require periodic maintenance to remove the collected debris collected in the catch basin. For this purpose access to the interior compartment of the catch basin is provided through removal of the grate covering the surface opening or a manhole cover where no such grate is present.
Storm water is frequently laden with trash, leaves and other organic debris, as well as sand, gravel, and other forms of sediment collected from streets, parking lots, and other paved areas. As storm water flows over a street or parking lot to a storm sewer, it also gathers other solid and fluid contaminants deposited on the surface, including oil, grease, fuel, hydraulic fluid, and metals from the vehicles that traverse these paved surfaces. Federal, state, and local standards for regulation of storm water runoff place ever-stricter limits on the discharge of organic, metallic, and other contaminants into downstream waterways. Storm water runoff that passes into many storm drains frequently fails to meet the applicable standards due to the excessive dissolved or suspended contaminants such as petroleum-based materials and metals that wash into the drains with the storm water. This problem has led to a plethora of prior art devices and systems for filtering and/or purifying storm water runoff water that passes into a storm drain.
One class of devices involves a barrier or other filter medium placed around, over, or on top of the drain opening at or above the surface level of the drain. Typical of such devices are those disclosed in U.S. Pat. No. 5,403,474, U.S. Pat. No. 5,632,888, U.S. Pat. No. 5,725,782, U.S. Pat. No. 6,010,622, and U.S. Pat. No. 6,749,366. In many of these prior art devices, the filters are placed or protrude above the level of the drained surface, creating an obstruction, or are only temporary installations designed to address acute runoff conditions during, for example, construction, etc.
In another class of devices, an absorbent filter medium is placed or suspended below the storm water inlet to filter and remove oil, grease, and other non-volatile organic contaminants that enter with the runoff. Such devices are exemplified in the disclosures of U.S. Pat. No. 5,820,762, U.S. Pat. No. 5,849,198, U.S. Pat. No. 6,368,499, and U.S. Pat. No. 6,872,029, as well as U.S. Patent App. Pub. No. US 2008/0023408 A1. Still another class of devices involves placing a basket or trap, alone or in combination with other filter devices and/or media, in or below the storm water inlet, as exemplified in the disclosures of U.S. Pat. No. 5,232,587, U.S. Pat. No. 5,284,580, U.S. Pat. No. 5,720,574, U.S. Pat. No. 6,080,307, U.S. Pat. No. 6,106,707, U.S. Pat. No. 6,287,459, U.S. Pat. No. 6,531,059, U.S. Pat. No. 6,797,162, U.S. Pat. No. 6,884,343, U.S. Pat. No. 7,083,721, U.S. Pat. No. 7,094,338, U.S. Pat. No. 7,270,747, and U.S. Pat. No. 7,922,916, as well as U.S. Patent App. Pub. No. US 2002/0057944 A1. Many of these devices have one or more drawbacks, including a bypass for overflow conditions that allows runoff to evade treatment entirely during excess flow conditions, or a catch mechanism formed of an open grate or mesh that allows small particulates and/or dissolved and suspended materials to pass unimpeded into downstream sewage systems and waterways.
More recently there has been a trend toward more complex systems using multiple filter media, incorporating plantings and other living materials, or having extensive underground mechanical operations. Such devices are exemplified in the disclosures of U.S. Pat. No. 6,277,274, U.S. Pat. No. 6,569,321, U.S. Pat. No. 6,719,910, U.S. Pat. No. 7,080,480, U.S. Pat. No. 7,625,485, U.S. Pat. No. 7,632,403, U.S. Pat. No. 7,638,066, U.S. Pat. No. 7,833,412, and U.S. Pat. No. 7,837,868, as well as U.S. Patent App. Pubs. No. US 2003/0047502 A1, No. 2006/0157423 A1, No. 2006/0163147 A1, No. 2008/0121579 A1, No. 2008/0121594 A1, No. 2008/0245710 A1, No. 2009/0039022 A1, No. 2010/0108617 A1, No. 2010/0150654 A1, No. 2010/0025313 A1, and No. 2011/0247973 A1.
A need therefore remains for a simple, effective filter device that can be retroactively fitted to a storm water inlet, wherein the device does not protrude or extend above street level or otherwise cause an obstruction on the surface being drained, that is capable of removing large objects, sediment and other suspended particulates, and metal and petroleum-based contaminants, and that does not allow storm water to bypass the treatment element entirely during any conditions. These needs are provided for by the present invention, as set forth in the description and claims that follow.